Sensory atypicalities represent a cardinal feature of Autism Spectrum Disorders (ASD) and have been established as the source of much behavioral aggression, frustration, and functional impairment over the course of the lifespan within this population[1-3]. Research in this area generally has been clinically focused, and limited to descriptions of the phenomena [4-8], although there are notable exceptions. These include a small number of psychophysics studies that report that, compared with neurotypical individuals, persons with ASD demonstrate a specific strength in their ability to detect small changes or differences between visual [9-14], auditory [15-21] and tactile stimuli [22-25]. In addition, emerging evidence from the basic neuroscience literature on distinguishing features of ASD highlights fundamental differences in the reliability of evoked responses to unisensory stimuli using fMRI [26], as well as differences in the timing [27, 28] and amount of multisensory integration [27, 29] using event- related potentials (ERP). Although both perspectives have advanced our knowledge of the field, what has been missing from the current literatures but which is now the focus of this proposal, is an integrated perspective on sensory processing in ASD. The series of studies proposed seeks to a) characterize the neurophysiological underpinnings of enhanced sensory perception across sensory modalities in ASD, b) assess the impact of enhanced sensory perception on the ability to integrate inputs from multiple sensory modalities at the level of both behavior and brain, c) to trace how these phenomenon unfold during development, d) to discern how attention shapes MSI in persons with an ASD, e) to ascertain if physiological indices of sensory processing and MSI can predict autistic symptomatology, and f) to determine if meaningful subgroups of individuals with ASD can be identified on the basis of the physiological and behavioral data. These goals will be addressed in 14 experiments in which the performance of individuals with an ASD (children and adults) will be compared to IQ- and age-matched typically developing children and adults. Children between the ages of 8 and 16 years, and adults age 18-30 will be tested to assess the developmental progression of sensory processing and MSI both in TD and ASD individuals from the school years into adulthood. By combining clinical (diagnostic, cognitive and behavioral) and experimental (psychophysics, reaction time, electrophysiology) methods to trace the development of sensory and multisensory processing and their relevance to clinical features of ASD, the proposed studies will yield evidence that is both clinically and functionally relevant. These findings may help identify physiological mechanisms that afford an integrated perspective on ASD and facilitate early objective diagnosis.